1. Technical Field
The present invention pertains to improvements in methods and apparatus for heating or cooling sterile surgical liquids and collecting surgical sterile slush. In particular, the invention is an improvement of the methods and apparatus disclosed in U.S. Pat. Nos. 4,393,659 (Keyes et al), 4,934,152 (Templeton), 5,163,299 (Faries, Jr. et al), 5,331,820 (Faries, Jr. et al), 5,333,326 (Faries, Jr. et al) and 5,457,962 (Faries, Jr. et al). The disclosures in those patents are expressly incorporated herein by reference in their entireties.
2. Discussion of the Prior Art
The above-referenced Keyes et al U.S. Pat. No. (4,393,659) discloses a surgical slush producing system having a cabinet with a heat transfer basin at its top surface. A refrigeration mechanism in the cabinet takes the form of a closed refrigeration loop including: an evaporator in heat exchange relation to the outside surface of the heat transfer basin; a compressor; a condenser; and a refrigeration expansion control, all located within the cabinet. A separate product basin is configured to be removably received in the heat transfer basin. Spacers, in the form of short cylindrical stubs or buttons, are arranged in three groups spaced about the heat transfer basin and projecting into the heat transfer basin interior to maintain a prescribed space between the two basins. During use, that space contains a thermal transfer liquid, such as alcohol or glycol, serving as a thermal transfer medium between the two basins. A sterile drape, impervious to the thermal transfer medium, is disposed between the product basin exterior and the liquid thermal transfer medium to preserve the sterile nature of the product basin. Surgically sterile liquid, such as sodium chloride solution, is placed in the product basin and congeals on the side of that basin when the refrigeration unit is activated. A scraping tool is utilized to remove congealed sterile material from the product basin side to thereby form a slush of desired consistency within the product basin. Some users of the system employ the scraping tool to chip the solid pieces from the basin side.
As noted in the above-referenced Templeton U.S. Pat. No. (4,934,152), the Keyes et al system has a number of disadvantages. In particular, the separate product basin must be removed and re-sterilized after each use. Additionally, the glycol or other thermal transfer medium is highly flammable or toxic and, in any event, complicates the procedure. The Templeton patent discloses a solution to these problems by constructing an entirely new apparatus whereby the product basin is eliminated in favor of a sterile drape impervious to the sterile surgical liquid, the drape being made to conform to the basin and directly receive the sterile liquid. Congealed liquid is scraped or chipped from the sides of the conformed drape receptacle to form the desired surgical slush.
The Faries, Jr. et al U.S. Pat. No. (5,163,299) notes that scraping congealed liquid from the drape is undesirable in view of the potential for damage to the drape, resulting in a compromise of sterile conditions. As a solution to the problem, the Faries, Jr. et al U.S. Pat. No. (5,163,299) proposes that the drape be lifted or otherwise manipulated by hand to break up the congealed liquid adhering to the drape. Although this hand manipulation is somewhat effective, it is not optimal, and often is inconvenient and constitutes an additional chore for operating room personnel.
The Faries, Jr. et al U.S. Pat. No. (5,331,820) resolves the problem of manual manipulation of the drape by providing a method and apparatus to automatically remove the congealed liquid adhering to the drape without endangering the integrity of the drape. A flat disk or plate is provided at the bottom of the basin under the drape. The plate is moved in an up and down manner to manipulate the drape and disengage the congealed liquid adhering to the drape. The plate may be attached to a mechanism below the basin, or to the drape itself as disclosed in the Faries, Jr. et al U.S. Pat. No. (5,457,962).
The Templeton U.S. Pat. No. (4,934,152) further provides an electrical heater disposed at the bottom of the basin to convert the sterile slush to warmed liquid, or to heat additional sterile liquid added to the basin. Templeton describes the need for such warm sterile liquid as occurring after a surgical procedure is completed to facilitate raising the body cavity of the surgery patient back to its normal temperature by contact with the warmed liquid. However, there are a number of instances during a surgical procedure when it is desirable to have simultaneous access to both the sterile warmed liquid and the sterile surgical slush. Accordingly, the Faries, Jr. et al U.S. Pat. No. (5,333,326) provides a method and apparatus for simultaneously providing surgical slush and warmed surgical liquid in separate basins during a surgical procedure using a single drape forming a drape receptacle within each basin.
The apparatus disclosed in the foregoing patents may stand some improvements to further ensure sterile conditions. Specifically, a sterile drape is typically disposed over a thermal treatment system having a basin recessed in a top surface of the system housing wherein a portion of the drape is pushed down into and conforms to the basin to form a drape container or receptacle for containing a sterile medium. The drape essentially forms a sterile field above the basin to maintain sterility of the sterile medium. Since the sterile surgical drape provides a sterile field above the basin for the sterile medium, it is important that a sterile drape be used for each procedure during system operation in order to prevent contamination of the sterile medium and serious injury to a patient. Although operating room personnel can be advised and cautioned about the importance of placing a drape over a thermal treatment system prior to the performance of a surgical procedure, there is no assurance that carelessness will not result in operation of a thermal treatment system without the use of a drape and thereby compromise the sterile field of an entire surgical procedure. Thus, it is desirable to ensure sterility of the sterile medium by enabling operation of the thermal treatment system only when a sterile surgical drape is positioned on the thermal treatment system.
Although the thermal treatment system disclosed in U.S. Pat. No. 5,653,938 identifies previously used drapes to control thermal treatment system operation by detecting a bar code affixed to or imprinted on drapes, the bar code identification is typically used only for drape detection purposes, thereby restricting bar code utilization potential. Further, since the bar code is affixed to or imprinted on the drape, the bar code is typically transferred onto material (e.g., drape material) that may not be optimal for containing the bar code, thereby possibly distorting the bar code and increasing the likelihood of erroneous identification. Accordingly, the bar code system disclosed in the aforementioned copending application may stand some improvement to further utilize the bar code identification for performance of various tasks, such as drape inventory, and to further dispose the bar code on a tag for attachment to the drape wherein the tag includes material (e.g., paper, cardboard, etc.) for containing the bar code that is conducive to proper bar code identification. Thus, there exists a need in the art for a thermal treatment system to ensure sterility of a sterile medium contained within a thermal treatment system basin by utilizing improved drape detection techniques that generally employ different types of drape indicators to detect the presence of the drape on the thermal treatment system in order to control thermal treatment system operation.